There is a continuous search for alternative modes of power generation since the last few decades, owing to various reasons, with the major being negative environmental effect of the use of fossil fuels and depletion of conventional resources. Renewable sources have gained wider acceptance for their use in power generation. However, their intermittent nature is a topic of concern. Intermittent renewables have generated interest in energy storage technologies. The primary purpose of the energy storage technology is to ensure quality and reliability of power supply. Thermal energy storage technology allows renewable energy, particularly solar energy, to be stored for later use. It also allows solar plants to be designed to optimize the electricity load profile according to the market needs. A solar plant with thermal energy storage technology can be designed, for instance, to continue electricity production even after sunset or to maximize electricity production during peak hours.

Molten salt energy storage, a mixture of 60% sodium nitrate and 40% potassium nitrate, stores energy at 566ºC in a hot molten salt storage tank until electricity is needed – day or night, with or without sunlight, during off-peak/normal operation hours or peak hours. Storage of energy in molten salt increases the overall reliability of solar plants, allows the plants to operate 24x7 providing baseload power for both on-grid and off-grid applications, increases the net annual output from a solar energy plant, helps avoid expensive fuel costs, and most importantly, provides cleaner power generation. The demand drivers for the molten salt energy storage projects are the increased adoption of renewable energy sources for power generation, and increasing need for the access to efficient, reliable, and price-competitive electricity. The global molten salt energy storage capacity stood at 1,288.5 MW in 2014 and is anticipated to reach 3,841.0 MW by 2018.

Large-scale Molten Salt Energy Storage Projects

280 MW Solana Generating Station (U.S.)

Located in Arizona, the U.S., the Abengoa’s Solana solar power generation plant has the gross turbine rated capacity of 280 MW. It was the first solar plant with thermal energy storage capabilities in the U.S. The plant employs parabolic trough technology that is used in conjunction with molten salt thermal energy storage. This enables it to generate electricity for additional six hours without the concurrent use of solar field. The molten salt storage technology allows energy to be dispatched as needed during cloudy periods and before sunrise or after sunset. This is the largest energy storage project and first of its kind in the U.S., to store over 1000 MWh of energy that can be dispatched upon demand without sunlight. This project is estimated to reduce Arizona’s need for fossil-fuel based power generation, would generate up to 1,095 TWh of clean renewable energy annually, and eliminate nearly 650,000 MT of CO emissions into the atmosphere each year. The deployment of this project would enable the state to contribute to the goals for renewable energy deployment and targets to reduce the negative impact of climate change. It is estimated that the deployment would also generate revenues between USD 300 million and USD 400 million in 30-year tax and more than USD 1 billion in gross state revenues.

110 MW Crescent Dunes Solar Energy Project (U.S.)

SolarReserve’s molten salt energy storage technology employed in the Crescent Dunes project, which is located in Tonopah, Nevada, the U.S., captures and stores solar energy to reliably provide electricity on demand. The project would provide electricity to 75,000 homes in Nevada 24x7 and in all climatic conditions. SolarReserve’s Crescent Dunes is about to be commissioned by the end of 2015. The project generated investment of more than USD 750 million in Nevada, the U.S. The molten salt energy storage technology allows 10 hours of full load storage, enabling energy generation when it is required the most.

150 MW Andasol 1 to 3 Solar Power Station (Spain)

Located in Andalusia, Spain, the Andasol Solar Power Station is the major thermal energy storage project in Europe. Solar Millennium AG initiated and developed the Andasol power plant. It is the first commercial parabolic trough project employing the molten salt thermal energy storage technology in the region. The Andasol solar power plant (phase 1 to 3) can store energy for around seven and half hours with the help of the molten salt storage technology. The annual operating hours of the solar power plant through thermal energy storage can almost be doubled, particularly in peak load conditions. This plant would reduce carbon emissions by 450,000 tons per annum compared to conventional coal-fired power plants.

Other Projects

Located in Pofadder, South Africa, KaXu Solar One is one of the major projects in the region. It is the first solar thermal electric plant to operate in South Africa. The plant started operating in early 2015. It employs parabolic trough technology with molten salt storage facility with the capacity to provide electricity for two and half hours. KaXu Solar One provides clean, sustainable power to approximately 80,000 households in South Africa and prevents CO emissions of 300,000 tons annually.

A total of about 2,125 MW of molten salt energy storage projects are in pipeline which are scheduled for deployment by 2018. China, Morocco, South Africa, Chile, and the U.S. have a large number of planned/under construction projects that are expected to be commissioned by 2018. Chile and South Africa have the highest capacity molten salt energy storage project under development. Xina Solar One (South Africa, 2017), Kathu Solar Park (South Africa, 2018), Bokpoort Concentrated Solar Plant (South Africa, 2015), Ilanga I (South Africa, 2017), Redstone Solar Thermal Power Plant (South Africa, 2018), Pedro de Valdivia (Chile, 2015), and Planta Solar Cerro Dominador (Chile, 2018) are some of the major projects in these countries. India also has three molten salt energy storage projects in pipeline, namely Diwakar CSP Plant (100 MW), Gujarat Solar One (28 MW), and KVK Energy Solar Project (100 MW).

Molten salt energy storage projects store energy for utilization after sunset or during the night. A few of the large market players have scheduled the deployment of their molten salt CSP plants in 2016 and years later in the U.S. Two such projects are Abengoa’s 500 MW Palen concentrating solar power (CSP) project and SolarReserve’s Rice Project in California, the U.S. These projects are stalled until the U.S. Government decides the future Investment Tax Credit (ITC) to be provided after 2016. The Investment Tax Credit (ITC) is one of the important federal policy mechanisms to support the deployment of solar energy projects in the U.S. The 30% ITC for solar energy is expected to drop to 10% at the end of 2016, and only those projects which are in operation at that time would qualify for this. Furthermore, as the ITC is expected to drop to 10% by the end of 2016, it does not give enough time to project developers to secure lands, permits, financing, and power purchase agreements.

About Pratik Sharma

Pratik is a self-driven writer with over 3 years of experience in the Energy industry. Currently, he is working as a Credit Analyst, with a focus on Global Energy and Commodities market, with Crisil Limited. Through his writing, he sheds light on Energy Storage, Smart Grid, and Alternative Energy Projects. He earned an MBA (Power Management) degree from the University of Petroleum and Energy Studies, and B.E. (Mechanical) from the Gujarat University.

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